As is generally known, various techniques have been proposed for improving wear resistance and seize resistance by forming a multilayer solid lubricant coating film on the surface of sliding members such as a skirt portion of pistons of automotive internal combustion engines.
As one example of those, the following Patent Publication 1, which has previously been filed by the applicant, discloses a technique of forming a solid lubricant coating film small in wear amount as an inner layer while forming a solid lubricant coating film large in wear amount as an outer layer thereby reducing unevenness of streaks remaining on the surface of a skirt portion to lower the friction between the skirt portion and a cylinder wall surface.